Towards Modeling Microglia Activation States in Brain Slice Cultures of AD relevant Pathology Brenda D. Moore1,2, Cara L. Croft1,2, Kaitlyn Rewis1,2, Tom B. Ladd1,2, Todd E. Golde1,2*, Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, University of Florida, Gainesville, FL; McKnight Brain Institute, University of Florida, Gainesville, FL *Corresponding Author
Recent gene wide association studies have identified rare genetic variants in genes associated with Alzheimer's disease (AD). Rare coding variants in microglial genes, such as, TREM2, PLCG2 and ABI3 have been implicated, however the role of these proteins in microglial function and effects on AD pathology remain unclear. Microglia have been challenging to study in vitro, in primary microglial cultures or immortalized lines as they assume a permanent activated state. This limits the interpretation of findings in these studies on the relevance to microglial changes in AD in humans. Likewise, microglia in organotypic brain slice cultures (BSCs) at DIV 7 are similar to other in vitro cultures of microglia showing an amoeboid activated state. However, we observed that after 1 month in culture microglia assume the morphology of quiescent in vivo-like adult microglia. This enables the study of microglia in a physiological relevant system, in an environment containing key central nervous system cell types. We have developed an assay to assess microglial phenotype and microglial clearance of amyloid-β in BSCs. We recently showed that a novel modified rAAV6 capsid triple mutant selectively transduced microglia in vivo and primary microglial cultures. We now show this rAAV selectively transduces microglia in BSCs. Using this system we can determine the roles of microglia through the use of knock out mice, manipulating microglia through overexpression of mutated genes by AAV transduction and pharmacologically to examine the effects on amyloid-β clearance. These studies will provide insight into the role of microglia in AD pathology and potentially highlight therapeutically relevant targets for AD.